This invention relates to the cleaving of single crystal semiconductor slices.
In the manufacture of semiconductor lasers it is known to make a two-dimensional array of such lasers on a slice which is cleaved up into bars each comprising a single line of lasers which is subsequently subdivided into dice each comprising a single laser chip. In the case of Fabry Perot cavity semiconductor lasers the optical cavity is located between a pair of plane parallel facets, and typically these plane facets are provided by the facets resulting from the cleaving operations that is used to divide the slice up into its component bars.
A known method of cleaving a semiconductor slice up into lasers first involves marking the edge of the slice to create localised damage from which to initiate a fracture, Such marks, hereinafter referred to as pack marks, are made at a spacing equal to the desired width of the bars. The marked slice is mounted on a plastics film stretched across a frame. The stretched film is lowered by hand on to a cleaving blade that is aligned with the desired cleavage plane of the slice and is registered with one of the peck marks, and the lowering is continued until such time as the slice cleaves along the line of the blade. The frame is indexed one bar width to the next peck mark, and is lowered once again on to the cleaving blade to repeat the cleaving process. With exercise of reasonable skill and attention this cleaving process is satisfactorily applied to the cleaving of bars up to approximately 2 cm long from a nominally 100 .mu.m thick InP/GalnAsP slice of laser devices, but is found progressively more difficult to achieve satisfactory yields as the length of the bars increases. The problem that is encountered with the cleaving of longer bars is the tendency for the cleave to have a number of terraces where the cleave is divided into a number of sections in which cleaving proceeds in the intended direction, these sections being linked staircase-fashion by much shorter sections in which the cleave has proceeded at right angles to the intended direction. These linking sections are undesirable because they detract from uniformity of laser cavity length for the members of any bar, and also because of yield problems associated with the chance of a linking section being formed in a region registering with the active part of a laser.